Message transmission system

ABSTRACT

An information transmission system for simultaneously transmitting baseband signals and broadband signals via a two-wire line between a central office and at least one subscriber. In one embodiment, a shared bidirectional splitter filter mounted on a circuit board communicates in one direction toward the subscriber over a subscriber line, and communicates in an opposite direction toward the central office. A baseband communication unit and a broadband communication unit are mounted on the circuit board, and at least one hybrid circuit is interposed between the filter and the baseband unit and broadband units. A central interface control unit is also mounted on the circuit board. The central interface control unit communicates in one direction toward the central office, and communicates in an opposite direction toward the baseband and broadband units. In another embodiment, the bidirectional filter is replaced with a plurality of unidirectional filters and a shared hybrid circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an information transmission system for thesimultaneous transmission of analog or digital baseband signals, forexample, POTS, ISDN, etc., and of broadband signals, for example ADSL,VDSL, etc., via a two-wire line from a central office, for example anautomatic exchange, to at least one subscriber, with a baseband unit anda broadband unit that are connected by at least one hybrid circuit andat least one broadband filter formed of a high-pass and a low-passfilter with the subscriber line.

2. Description of Related Art

At the present time, known systems of this type exist, for example, inautomatic exchanges of the public telephone network, whose operatorsoffer broadband transmission capability for certain subscribers, asneeded. But broadband service can be provided to subscribers not only inautomatic exchanges but also in remote automatic exchanges connected tothe former via a transmission link.

Broadband technologies, such as ADSL, VDSL, and xDSL, etc. use thefrequency band above the baseband, which is used, for example, by POTS(Plain Old Telephone) or ISDN signals. These various transmissionservices use the same subscriber line as the transmission medium.

To give an example, the ADSL (asymmetric digital subscriber line)broadband transmission technology, which is becoming more and morepopular, enables digital information transmission of large volumes ofdata via a two-wire subscriber line in one direction from the centraloffice to the subscriber and the transmission of control functions inboth directions. Currently, ADSL information transmission systemsfrequently use QAM technologies, for example DMT (discrete multiple tonemodulation) or CAP (Carrierless phase modulation), whereby the formedsignals overlie the analog or digital telephone signals, for example,POTS or ISDN, with respect to frequencies. The signal transmitted or tobe transmitted is split via special broadband filters (ADSL filters) forreceiving and superposed for transmission, both on the exchange side andthe subscriber side.

At the central office, for example, the automatic exchange, the basebandunit, the broadband unit, and their common broadband filter are arrangedseparate from each other in different spatial areas; the differenttransmission units in the past were considered to be completely separatefunction blocks, which therefore also sometimes were arranged at pointsfar apart within the automatic exchange.

The disadvantage of known information transmission systems of this typeis therefore that the spatial separation results in significant wiringexpenditures and requires additional space because of separate filterassemblies and separate racks for broadband or baseband units. Wiringexpenditures hereby include not only the actual cross-connection workwithin the automatic exchange but also the documentation of how theindividual, installed lines are associated with the interconnectedunits. These records constantly must be adjusted to the changes that aregradually made over time and require the archiving of data andmaintenance of the archived data.

This means that the additional cost of maintenance resulting from eachwiring, which manifests itself especially in personnel costs, is veryimportant. The costs for the individual cross-connection points withinthe automatic exchange are also significant.

Another disadvantage is due to the fact that a separate processorcontrol must be provided both for the broadband unit and for thebaseband unit.

The objective of the invention is to describe an informationtransmission system of the initially mentioned type, which enables areduction in the required space and wiring expense at the centraloffice, especially with respect to cross-connecting and maintenancework.

Another objective is to reduce the preventive maintenance expense andequipment costs, for example, for cross-connection points, of thesystem, and of the number of individual interface controls for thesystem.

Another objective of the invention consists of creating an informationtransmission system in which existing transmission units can be easilyadapted to additional, new ones.

BRIEF SUMMARY OF THE INVENTION

According to the invention this is achieved in that the baseband unit,the broadband unit, if required, the one (at least) hybrid circuit, andthe one (at least) broadband filter are combined in one unit with acentral interface control device.

This permits a centralized coordination of the operation and maintenanceof the individual, different units. It is, for example, always knownwhich type of transmission system the existing subscriber uses. If thesubscriber now would like to upgrade an additional ADSL transmissionunit in addition to its already existing POTS or ISDN unit, the correctbroadband filter for the subscriber can be immediately provided, and theADSL unit can be correctly configured. Another advantage is that thebroadband filter can be adapted to the already existing properties ofthe POTS or ISDN units. If required by the connection of a certainbroadband filter, even the POTS configuration can be readjustedcorrectly. The reason for this is that different telephone networkproviders specify specific real or complex line impedance levels fortheir POTS subscribers, which require, for example, an active broadbandfilter. If the POTS configuration is changed to purely real impedance,however, a passive broadband filter is sufficient.

Other advantages are the reduced maintenance and wiring expendituresachieved by the consolidation of the separate units, since this requiresless related wiring work and cable maintenance. The reduced need fordocumentation resulting from this is another advantage of thecommunication system according to the invention. The central interfacecontrol eliminates the need for the additionally required, separatecontrols. It combines the otherwise separate controls; i.e. only oneconnection to the central office control is required, while the separaterealization requires at least two connections.

In a particular preferred manner, one possible embodiment of theinvention provides that the baseband unit, the broadband unit, and, ifnecessary, the one (at least) hybrid circuit, and the one (at least)broadband filter are combined on the same circuit board. This makes itpossible to effectively use the advantages of combining baseband andbroadband units.

In a further possible embodiment of the invention, the transmissionoutput and reception output of the broadband unit or baseband unit areconnected to the subscriber inputs or outputs of one each unidirectionalbroadband filter, and that the input and output of the twounidirectional broadband filters are connected with a common hybridcircuit.

Based on the special arrangement of this embodiment, the twounidirectional broadband filters are moved directly to the ADSL or POTSinput, resulting in further reduction of the technical expenditure andcosts. This avoids the otherwise necessary bidirectionality for thebroadband filter, and instead, two unidirectional broadband filters areused, which can be installed with significantly less technicalexpenditure and therefore also at lower cost. Another factorcontributing to this is that this reduces the requirements with respectto dielectric strength. In addition, each broadband filter can beoptimized independently.

In another embodiment of the invention it may be provided that thecommon hybrid circuit, the two unidirectional broadband filters, thebroadband unit, the baseband unit, and the central interface controldevice are all combined on one circuit board.

The arrangement on a common circuit board has the direct advantage thatthe signals transmitted on the subscriber line can be adapted better tothe used transmission types. The various transmission services thereforeare influenced less by call metering signals and calling signals.

According to another embodiment of the invention, the digital signalprocessor circuits associated with the baseband unit and the broadbandunit can be combined into a central, digital signal processor circuit,resulting in a significant reduction in required components forfiltering and encoding in the baseband and broadband unit.

According to another embodiment of the invention, it may be providedthat the analog-to-digital converters associated with the baseband unitand the broadband unit are combined into a central analog-to-digitalconverter. This also permits a clear reduction in the cost ofcomponents.

According to another embodiment of the invention, it may be providedthat the baseband unit, the broadband unit, the central interfacecontrol device, and possibly parts of the broadband filter(s) can be atleast partially integrated. The integrated circuit hereby may beconstructed as one component or a multi-component chipset.

This makes it possible to miniaturize individual units, and thus achievea further reduction in space. By combining the devices for controlling,for analog-to-digital conversion, and for filtering for the baseband andbroadband unit into one each functional unit also enables a significantreduction in energy losses. Compared to standard solutions, theintegration also further reduces the total manufacturing costs andwiring expenditures. The following describes the invention in detail inreference to the embodiments shown in the drawings, whereby:

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a block switching diagram of an information transmissionsystem according to the state of the art;

FIG. 2 shows a block switching diagram of an embodiment of theinformation transmission system according to the invention;

FIG. 3 shows a block switching diagram of another embodiment of theinformation transmission system according to the invention;

FIG. 4 shows a graph with the frequency ranges occurring on thetransmission line of an information transmission system;

FIGS. 5 and 6 each show a block switching diagram of a subscriberinterface circuit for a baseband and a broadband unit according to thestate of the art; and

FIG. 7 shows an information transmission system with broadbandtransmission according to the state of the art.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an information transmission system for the simultaneoustransmission of analog or digital baseband signals, for example, POTS,ISDN, etc., and of broadband signals, for example ADSL, VDSL, xDSL,etc., via a two-wire line 4 according to the state of the art, which islocated at a central office, in this example in an automatic exchange.Such a central office could also be a private branch exchange, a remoteautomatic exchange, or a similar installation.

A baseband unit 3 through which the analog voice signals, for examplePOTS, or digital information, for example ISDN, of the telephone networkis sent to or received by the connected subscriber at the other end ofthe subscriber line 4 is controlled via an interface control device 6which again is connected to a central office control. The drawn-in nodes10 are cross-connections in the main distributor of the automaticexchange, but which do not affect the function of data transmission.They are therefore not shown in FIG. 3. The baseband unit 3 exists forall subscribers that can be connected via the respective automaticexchange. As an additional transmission possibility, each subscriber, asrequired, also may be assigned a broadband transmission unit 2 whosefunctions are monitored via another interface control device 5.

A block switching diagram of the internal construction of a basebandunit 3 is shown in FIG. 5, and that of a broadband unit is shown in FIG.6.

To split the frequency ranges of the superposed signal that comes in viasubscriber line 4, a bidirectional broadband filter 1 is provided thatis connected on one side with the subscriber line 4 and on the otherside with the inputs or outputs of the baseband unit 3 and broadbandunit 2. The signals sent by units 2 and 3 in the opposite direction aresuperposed in the broadband filter with respect to frequency and aretransmitted to the subscriber. The frequency bands of POTS, ISDN, andADSL signals occurring hereby are shown in FIG. 4.

The internal structure of a broadband filter 1 is shown in FIG. 7,whereby a bidirectional broadband transmission system 15 is connectedvia a high-pass filter 110, and ISDN and POTS units are connected via alow-pass filter 12 with a subscriber or local line 4. The dielectricstrength of the high-pass and low-pass filter 110, 12 must be designedfor the actually occurring calling and supply voltages.

Since the broadband unit 2 in FIG. 1 represents an additional servicethat may be chosen by the subscriber, it is located at another place inthe automatic exchange than the baseband unit 3, for example, on anotherfloor. The broadband filter 1 is also located separately from the otherunits in its own filter racks. This results in wiring and maintenanceexpenditures that this invention attempts to eliminate. An adaptation ofthe various services and of the broadband filter is also often verycomplicated since the locally separated units must be adapted to eachother in a suitable manner.

One embodiment of the invention is shown in FIG. 2, whereby hybridcircuits 7-8 not shown in the block switching diagram of FIG. 1 butwhich must be present there too (also see FIG. 5,6) that are requiredfor operating the information transmission system are interposed betweenthe baseband unit 30 or broadband unit 20 and the filter 1.

According to the invention the baseband unit 30, broadband unit 20,hybrid circuits 7, and common broadband filter 1 are combined into oneunit with a central interface control 50. This places all of thesefunctional units directly next to each other, preferably on a commoncircuit board. The dotted line around the units indicates this. Thispermits a significant reduction in the wiring and maintenance work anddocumentation expenditures, as well as the possibility of individualadaptation to existing line standards and filter types.

Another improvement to the system according to the invention can beachieved with the embodiment according to FIG. 3, since instead of abidirectional filter several unidirectional filters are provided whichare constructed at significantly lower cost. For this purpose, thetransmission output 22, 24 and the reception input 23, 25 of thebroadband unit 20 or baseband unit 30 are connected on the subscriberside with inputs 42, 43 or outputs 44, 45 of one each unidirectionalbroadband filter 1′, 1′″ or 1″, 1 ^(IV).

Input 51 and output 53 of the two unidirectional broadband filters 1′,1′″ or 1″, 1 ^(IV) furthermore are connected with a common hybridcircuit 25. This separates the filter function into the two transmissiondirections and combines the hybrid circuit function into a functionalblock.

In order to achieve further simplification, the common hybrid circuit25, the two unidirectional broadband filters 1′, 1′″ or 1″, 1 ^(IV), thebroadband unit 20, the baseband unit 30, and the central interfacecontrol device 50 are combined in FIG. 3 on one circuit board 11.

Another degree of unifying the combined units can be achieved if thedigital signal processors (DSP) in the baseband unit 30 and broadbandunit 20 can be combined, so that, for example, filtering and signalgeneration can be accomplished with a single DSP. In a similar manner,digital-to-analog converters and analog-to-digital converters of thebaseband unit 30 and the broadband unit 20 in an integrated circuit alsocan be used several times.

To illustrate this, FIGS. 5 and 6 each show a CODEC 42 for a basebandunit and a CODEC 52 for a broadband unit in the form of a blockswitching diagram, whereby in addition to a bidirectional encoding unit45, 55 and a bidirectional filter 44, 54 one each analog-to-digital ordigital-to-analog converter, 43 and 53 respectively, are provided, andtheir converter function could be combined in the informationtransmission system according to the invention in a centralanalog-to-digital or digital-to-analog converter. In the same way, eachof the digital signal processors provided for filtering in filters 44and 54 can be combined in a central digital signal processor.

Finally, a further improvement of operating conditions can be achievedin that the baseband unit 30, broadband unit 20, central interfacecontrol device 50, and, as required, parts of the broadband filter 1(FIG. 2) or broadband filters 1′, 1′″ or 1″, 1 ^(IV) (FIG. 3) are atleast partially integrated or constructed as an integrated circuit. Theintegrated circuit hereby can be constructed as a component or as achipset consisting of several components.

1. An information transmission system for simultaneously transmittingbaseband signals and broadband signals via a two-wire line between acentral office and at least one subscriber, said system comprising: ashared bidirectional splitter filter mounted on a circuit board, saidfilter communicating in one direction toward the subscriber over asubscriber line, and communicating in an opposite direction toward thecentral office; a baseband communication unit mounted on the circuitboard; a broadband communication unit mounted on the circuit board; atleast one hybrid circuit mounted on the circuit board interposed betweenthe filter and the baseband unit, and between the filter and thebroadband unit; and a central interface control unit mounted on thecircuit board, said central interface control unit communicating in onedirection toward the central office, and communicating in an oppositedirection toward the baseband and broadband units.
 2. The informationtransmission system of claim 1, wherein the baseband unit and thebroadband unit each have an associated signal processing circuit, andthe signal processing circuit for the baseband unit is combined with thesignal processing circuit for the broadband circuit in a central digitalsignal processor circuit mounted on the circuit board.
 3. Theinformation transmission system of claim 1, wherein the baseband unitand the broadband unit each have an associated analog-to-digitalconverter, and the analog-to-digital converter for the baseband unit iscombined with the analog-to-digital converter for the broadband circuitin a central analog-to-digital converter mounted on the circuit board.4. The information transmission system of claim 1, wherein the basebandunit, the broadband unit, and the central interface control unit are atleast partially integrated into a single integrated circuit on thecircuit board.
 5. The information transmission system of claim 1,wherein the integrated circuit is constructed as a single component or amulti-component chipset.
 6. An information transmission system forsimultaneously transmitting baseband signals and broadband signals via atwo-wire line between a central office and at least one subscriber, saidsystem comprising: a shared hybrid circuit mounted on a circuit board,said hybrid circuit communicating in one direction with the subscriberover a subscriber line, and communicating in an opposite direction withthe information transmission system; a baseband communication unitmounted on the circuit board; a broadband communication unit mounted onthe circuit board; a plurality of unidirectional low-pass and high-passfilters mounted on the circuit board, wherein the low-pass filters areinterposed between the shared hybrid circuit and the baseband unit, andthe high-pass filters are interposed between the hybrid circuit and thebroadband unit; and a central interface control unit mounted on thecircuit board, said central interface control unit communicating in onedirection with the central office, and communicating in an oppositedirection with the baseband and broadband units.
 7. The informationtransmission system of claim 6, wherein two unidirectional low-passfilters, passing information in opposite directions, are connected tothe baseband unit, and two unidirectional high-pass filters passinginformation in opposite directions are connected to the broadband unit.8. A circuit for transmitting baseband signals and broadband signals viaa two-wire line between a central office and a subscriber, said circuitcomprising the following elements mounted on a single circuit board: ashared hybrid circuit communicating in one direction toward thesubscriber over a subscriber line, and communicating in a oppositedirection toward the central office; a baseband communication unit; abroadband communication unit; a first unidirectional low-pass filterinterposed between the shared hybrid circuit and the baseband unit, saidfirst unidirectional low-pass filter passing information in thedirection toward the subscriber; a second unidirectional low-pass filterinterposed between the shared hybrid circuit and the baseband unit, saidsecond unidirectional low-pass filter passing information in thedirection toward the central office; a first unidirectional high-passfilter interposed between the shared hybrid circuit and the broadbandunit, said first unidirectional high-pass filter passing information inthe direction toward the subscriber; a second unidirectional high-passfilter interposed between the shared hybrid circuit and the broadbandunit, said second unidirectional high-pass filter passing information inthe direction toward the central office; and a central interface controlunit interposed between the central office and the baseband andbroadband units, said central interface control unit communicating inone direction toward the central office, and communicating in anopposite direction toward the baseband and broadband units.